1. Field of the Invention
The present invention relates to a spray system resonance frequency modulation technology, and more particularly, to a micro-spray system resonance frequency modulation method and device.
2. Description of Related Art
Spray systems have been in use for years. As regards the oldest spray system, liquids are atomized mostly by means of pressurized gases. However, as technology advances, technological/engineering systems are becoming more miniaturized and more energy-saving so as to be increasingly efficient and compact, resulting in the use of actuators made of piezoelectric materials in a micro-spray system for atomization. A piezoelectric micro-spray system nowadays is typically miniaturized and energy-saving to such a great extent that it is in wide use, for example, micro-cooling units used in computers to achieve heat dissipation. Owing to the demand for ever-increasing computer speed and functions, CPU has to work faster and faster, which in turn brings about a surge of power consumption and heat generation. To cope with this, a micro-spray cooling system replaces a conventional fan cooling system in dissipating heat generated by computer, so as to enhance cooling efficiency. In addition, a nebulizer, a product of biotechnology, medicine and pharmacy, rely upon a piezoelectric micro-spray system for reducing the size of medication to micro-dimensions such that a drug can be inhaled via the oral-nasal route and subsequently be delivered to and absorbed by the lungs. The above-mentioned are typical examples of the application of a micro-spray system to engineering.
A piezoelectric micro-spray system is operated mostly at resonance frequency and thereby is characterized by considerable vibrational energy; as a result, a piezoelectric micro-spray system is characterized by relatively great flow and great spray area, which accounts for plenty of heat it dissipates when used in a cooling system and great amount of medication it atomizes when used in a medication atomization system. By contrast, with a piezoelectric micro-spray system operating at resonance frequency, material impedance is relatively low, and thus the required current is low enough to allow the piezoelectric micro-spray system to be energy-saving. However, the resonance frequency at which a piezoelectric micro-spray system works is susceptible to ambient factors (for example, temperature), boundary conditions, and a package process; hence, both resonance frequency difference and resonance frequency drift may occur, undermining the system's efficiency and stability.
As disclosed by U.S. Pat. No. 6,422,080, a piezoelectric actuator used in a disc drive system is susceptible to a spring load and a gluing process, thus resulting in resonance frequency changes. Considering that a disc drive system should avoid structural resonance in order to ensure the correctness and stability of data access, the aforesaid patent proposes minimizing vibrational resonance or inhibiting resonance through prevention of the appearance of resonance nodes, by adjusting the extent to which a pivot is fastened to an actuator assembly.
U.S. Pat. No. 5,805,028 was taken out in an attempt to solve the underlying problems of a related system, that is, resonance frequency varies with ambient temperature, and the resonance frequency drift results in decreased efficiency and increased power consumption and accounts for the heat generated by materials. To address the aforesaid problem, U.S. Pat. No. 5,805,028 proposes using a circuit for changing output parameters as well as output temperature-compensated voltage and frequency. Similarly, U.S. Pat. No. 6,819,027 proposes using a circuit to detect resonance frequency and keep the system working at resonance frequency. U.S. Pat. No. 6,569,109 proposes detecting phase difference in a real-time manner with a phase difference detection circuit, and calculating resonance frequency to be outputted in response to ambient variations, using a resonance frequency detection circuit and initial resonance frequency, with a view to coping with the frequency drift problem.
However, all the available problem-coping methods involve using a complicated circuit designed to solve the problem of resonance frequency drift rather than performing simple calibrating work designed to achieve resonance frequency modulation, for example, changing output parameters in a circuit-controlled manner, detecting resonance frequency, manipulating control circuit output and maintaining an intended range of resonance frequency in a circuit-controlled, circuit-feedback manner, with a view to controlling a system and thereby allowing the system to work at resonance frequency, and, alternatively, detecting voltage phase difference, and calculating resonance frequency to be outputted in response to ambient variations, using a resonance frequency detection circuit and initial resonance frequency.
The aforesaid patents propose using mostly a control circuit for operating a system at resonance frequency that differs before and after operation; hence, a micro-spray system functioning in accordance with the prior art demonstrates flow variations or other changes and therefore increased system uncertainty.
Therefore, an existing issue which relates to a micro-spray system and needs urgent resolution involves solving the drawbacks of the prior art, developing a micro-spray system on which frequency correction may be performed before operation and resonance frequency modulation may be performed during operation with a view to increasing spray flow and spray area and minimizing the effect of ambient factors.